Handling of fluorine



March 8, 1960 H. R. NEUMARK ET 2,927,438

HANDLING OF FLUORINE w Filed Aug. 8, 1957 v 2 Sheets-Sheet 1 INVENTORS HANS R.NEUMARK b JOHN M.S1EGMUND BY ATTORNEY March 8, (1960 H. R. EUMARK ET AL 2,927,438

HANDLING OF FLUORINE Filed Aug. '8, 1-957 Sheets-$heet 2 INVENTORS HANS R. NEUMARK JOHN M.SIEGMUND ATTORNEY United States Patent 2,927,438 HANDLING OF FLUORINE Hans R. Neumark, Summit, and John M. Sie gmund, "Elizabeth, NJ., assignors to Allied Chemical Corporation, a corporation of New York r ea an u s 8, Se a N 6 ,0 11 Claims. or. 52-55 The present invention relates to the placing of fluorine in stationary or transported storage and its discharge from storage. Elemental fluorine, a diflicultly condensable very highly reaotive gas boiling at 187-. C., is ordinarily produced as gas by electrolysis of sodium fluoride and is not condensed during any portion of its production and purification as is the case with the low boiling gases, such as air, nitrogen, oxygen and the like, which are available on the market in liquid form. Accordingly, heretofore fluorine has been handled for and during shipment as a compressed gas in heavy walled metal cylinders. Such cylinders are heavy and of limited capacity for fluorine. Their use is sufflciently expensive to discourage, if not to make entirely impracticable economically, the use oflarge quantities of fluorine at a point remote from thatof its generation.

In order to meet safety requirements for shipment and handling the weight ratio of the metallic cylindrical containers to content of PI ssurized gaseous fluorine has been ordinarily greater than 30:1 and the containers or bottles have been of quite limited size, containing ten pounds or less of the gasat pressures up to aboutfour hundred pounds per square inch.

It is an object of the present invention to store and transport elemental fluorine as-bulk liquid. Another obtea is to provide for the economical, safe storage, transportation and other handling of flurine in largequantities without the use ofhigh pressures. Another object is to effect rapid transfer of fluorine to and from storage facilities while achieving the foregoing objects. Another object is to provide relatively simple equipment for achieving the other objects of the invention. Still further objects and advantages of the invention will be apparent from the description thereof which follows.

In accordance with certain aspects of the invention, fluorine gas at low pressure, for exampleat the slight superatmospheric pressure obtaining at the discharge of sodium fluoride electrolytic cell installation of'a fluorine. plant, is admitted to an extended heat exchange passageway disposed within a body of liquid lower boiling than fluorine. The gaseous charge then flows through the extended passageway until condensed and cooled to temperature such that its vapor pressure is substantially below atmospheric, preferably one-half an atmosphere-or less. Resulting condensate at sub-atmospheric pressure is then admitted to a suitable evacuated storage, Volume provided within a receptacle such as a tank, preferably at a'l'evel substantially above its bottom, which is also im-. mersed in the body'of low. boiling liquid until the desired liquid level in the receptacle has been reached. Simulta'i'loilslh With e. h n f he. evacuat d tank, the uquia lowenhoiling fluorine is replenished oontin-l assay or nominees to time as may be necessary to maintainijhe extendedpassageway and preferably the'tank; completely or substantially completely. immersed therein,

Wh n it is de ed. dis her'se e o ne om. e tank, with. or without intervening in. transportationof; it and the bodyof low boiling liquid, a gaslower boiling 2,927,438 Patented Mar. 8, 1960 than that liquid and inert with respect to fluorine is con ducted into the tank, preferably through the extended passageway to. exert pressure on the liquid fluorine content and force it through an outlet communicating with the tank bottom and extending to a suitable receptacle therefor where it may be stored as liquid for subsequent use as such or be allowed to vaporize for use in the vapor state.

During storage and transportation, the liquid fluorine is at pressure substantially lower than the pressure of the Surrounding body of low. boiling liquid, which preferably is maintained at atmospheric pressure, so that any dam: age to the fluorine storagetank could not result in loss of this highly reactive toxic material to the atmosphere. Rather a rupture. of the tank for any reason would result in flow ofthe cooling liquid into the liquid fluorine. Ac.-. cordingly, the cooling liquid is preferably one which is inert chemically with respect to, as well as being lower boiling than, the fluorine. The preferred material for this purpose for these reasons, in addition to economy, is liquid nitrogen. Although less desirable, liquid air may he used as coolant or mixtures of liquid oxygen and liquidnitrogen boiling at or below about l C. Additions ally, the gas used to effect discharge of the fluorine must be inert with respect to this chemical in addition to being lower boiling than coolant. The preferred material for- Neon is also satisfactory as a but whether of this shape or another, the center or axis of the inner tank is preferably below that of the outer in order to provide for a greater volume of coolant above than below, the inner tank to provide for evaporation of a maximum portion of coolant while maintaining the tank completely immersed therein. The outer tank is enclosed by a third container or shell spaced preferably equidistantly therefrom, the intervening space being filled with suitable insulation and preferably being evacuated.

A feed conduit interconnects the interior of the fluorine tank preferably at the upper portion thereof and a valvedg fluorine inlet disposed outside the assembly. This conduit provides as, an intermediate portion thereof, disposed within the space for liquid coolant, an elongate heat ex change passagewayof length sufficient to effect condensa-:

tion of fluorine charge audits further cooling to approxi-. mately. l quid coolant temperature. The elongate pas-l sageway is usuallyof length of at least half, as up to one and one-half times the length of-the periphery of the fluorine tank, and preferably is disposed at or below the; center or axis of that tank/ The heat exchange portion, conveniently but notnecessarily takes the form of a coilextending around the major portion of the tank periphery.

Extending between the bottom of the interior of th inner tank and a valved discharge outlet outside of the assembly i s.a conduit for discharging the pressurized.

Communicating between the second tank, 1

liquid fluorine. preferably at its top, and a-valved inlet disposed outside of the assembly'is a conduit for admitting coolant Each of the conduits referred to passes in fluidtight relation-j I ship through the walls enclosing containers.

Referring to the drawings, Figure 1 is a sectional eleof the coolantand insulation:

vation illustrating a preferred assembly for practice of" the invention and Figure-2 is an. end elevation of the" right or service. end of the assembly of Figure 1,. certain parts being shown broken away for clarity.

Referring ,to Figure -1,,the horizontally disposed. assenn:

bly, comp-rising nested tanks 10, 11 and 12, respectively,

which are preferably sealed from the atmosphere and from one another except for the conduits and connections described hereinafter, enclosing in the order named insulating space 13, coolant volume 14 and liquid fluorine storage space 15, together with a service assembly of valved supply and discharge conduits and indicating instruments (described hereinafter in more detail) housed within extension 16 of the walls of outer tank 10, constitutes a unit which is suitably mounted on a fixed foundation, on the bed of a railroad car, or on a motor vehicle chassis. Outer shell and tank 11 are preferably concentric as shown and so dimensioned as to provide three or more inches of space entirely therearound for insulation 17, which may be perlite or other suitable fluent, preferably light, solid insulating material capable of being charged to the insulating space by one or more charge ports such as flanged nipple 18. The filled insulating space may be and preferably is maintained under vacuum imposed, for example, through valved conduit 19 extending into the insulating space and terminating as an open ended filter chamber 20 containing glass wool or other suitable packing to prevent removal of finely divided insulation during the evacuating procedure.

Innermost tank 12 is, as shown, preferably supported so that its axis is appreciably below the axis of liquid coolant container 11 and is so proportioned in size with respect to the latter as to occupy at least half and up to three-quarters or more of its total volume. Any desired method of supporting the respective containers within one another may be employed which keeps within reasonably low limits the rate of heat conductivity from the inner receptacles to the outside of the assembly. One satisfactory method indicated diagrammatically is the use between receptacles 10 and 11 of support members or blocks 21 having adequate structural strength and insulating properties, for example, phenol-formaldehyde, urea-formaldehyde, melamine-formaldehyde or other suitable molded resin or a laminate, the blocks having, as indicated in Figure 2, arcuate upper and lower edges to conform to the shapes of the receptacles. Inner tank 12 may be similarly supported by suitable insulating pillowblocks 22 resting on coolant receptacle 11. A portion or all of the weight of either or both of the inner tanks may be supported ultimately from outer receptacle 10 in known manner by suitable thin rods extending between brackets fastened to the exterior of the tank being supported and to the interior of the supporting tankor shell.

Connecting the interior of innermost or fluorine tank 12 and inlet port 23 is elongate heat exchange member and charge conduit 24 containing valves 24a disposed adjacent its inlet end. The major portion 24b of conduit 24 is an extended heat exchange passageway shown as being in the form of a hairpin bend or loop extending for most of the length of tank 12 and around its end at such height, preferably not above the axis of intermediate tank 11, as to be completely immersed in liquid coolant when the latter somewhat less than half fills the space between the tanks. The intermediate or heat exchange portion of conduit 24 may assume other shapes such as, for example, a pancake coil or a series of hairpin loops disposed below innermost tank 12 or at either or both sides or ends thereof, but preferably completely below the axis of intermediate tank 11.

Connecting the bottom of the interior of tank 12 and a fluorine discharge port 25 is fluorine discharge line 26 containing valves 26a disposed near its outlet end. This line need not, and preferably does not, provide an extensive heat exchange passageway within the coolant volume. Tapped into fluorine .charge line 24 at any desired point, e.g. outside outer tank 10, as shown, is vapor line 27 leading in known manner to pressure gauge 28 for indicating the pressure of the interior of fluorine tank 12. Charge and discharge lines 24 and 26am preferably the only means of fluid communication between tank 12- and its surroundings.

Interconnecting the interior of tank 11, preferably at its top and inlet 29 for liquid coolant is coolant charge line. 30 provided with valve 30a disposed adjacent its inlet end. Interposed between the valve 30a and the coolant inlet to tank 11 is vent line 31 which preferably terminates in a one-way automatic relief valve 32 adjusted to release at substantially atmospheric pressure coolant gas resulting from evaporation of liquid coolant. Pressure gauge 33 is connected, as by a tap line 34, with coolant charge line 30 at any desired point, e.g. through coolant vent 32, as shown, to provide visual indication of the pressure of coolant gas within tank 11; Pressure gauge 35 and line 36 extending into the bottom of the interior of tank 11 are provided so that, in known manner, there may be visual indication of the quantity of liquid coolant in tank 11 by means of its hydrostatic head.

' In charging the assembly with liquid fluoride in accordance with the invention, coolant charge line 30 is con nected to a source (not shown) of liquid coolant lower boiling than fluorine, e.g. nitrogen, which is then forced into tank 11 until the coolant level is above conduit section 2412 and preferably until tank 11 is filled. Before, during or after charging of the equipment with coolant, tank 12 is preferably evacuated by means of a vacuum purge pump connected to either fluorine inlet 23 or fluorine outlet 25. While tank 11 remains connected to the source'of coolant, fluorine inlet port 23 is connected to a source (not shown) offluorine vapor at atmospheric or somewhat higher pressure, e.g. the storage containers of a battery of electrolytic fluorine cells, the valves 24a being open and valves 26a closed. The gaseous fluorine is allowed to flow, through charge port 24, includingthe heat exchangesection thereof immersed in the coolant where it condenses, is cooled to the boiling point of the coolant, and then, as condensate, into the top of tank 12 which also is at coolant boiling point. This operation is continued either until the desired measured quan-' tity of fluorine is admitted to the assembly or until fluorine flow ceases, at which time valves 24a are closed and the source of gaseous fluorine disconnected. In this manner tank 12 may be charged with fluorine until or somewhat more filled.

During charging of the fluorine as described above, liquid coolant evaporates as a result of transfer of heat from the walls of containers 11 and 12 and of absorption by it of heat of condensation of liquid fluorine, the gaseous coolant medium exiting the equipment by vent line 31 and vent valve 32. From time to time or continuously, additional coolant is supplied through line 30 to maintain at least the heat exchanger section 24b of charge conduit 24 and preferably .the entire tank 12 immersed in coolant. Admission of nitrogen is regulated either manually or automatically to maintain the required liquid level as indicated on gauge 35. When the fluorine charging is completed tank 11 is preferably completely filled with coolant.

During subsequent sationary storage or transporta tion of equipment charged with liquid fluorine in accord ance with the invention, the coolant evaporates only at the rates equivalent to the heat losses through the outer insulation, and the fluorine remains liquid at sub-' atmospheric pressure usually of a half atmosphere or less (absolute pressure of the order of five pounds per square inch when nitrogen is the coolant) until substan tially all the coolant is evacuated.

of liquid eseleat- D a s to age of the liquid fluorine.

In typical installa tions used on truck chassis when ambient daytime tenij-j peratures of 90 F. to F. and above are reached.

5. p 12 remains completely sealed from the surrounding elements of the assembly and fromthe' atmosphere; "Once a unit embodying practiceof'the' invntiio is placed. into service it is "notneeessary to remove liquid coolant from it upon discharge'of'the fluorine. It 'is, in fact, preferred'to utilize the'cooling, effect or the coolant between periods ofclia'rging "WitK'fluorine, as when;

tank

trailer, motor vehicle or railroad car carrying the'a'ssem b ly is' being returned frompo'int of delivery to fluoirne plant, to minimize coolant requirements during the sub sequent charging operation. Appropriately" and practicably sized equipment containing nitrogen in volume no more than half the volume'of'liquid fluorine retains liquid coolant and remains atliquid cool'ant temperature without additional charges or coolant sufficiently long to permit intercontinental shipment an aeuv eriy'or the fluorine and return'of the'assemblytopoint forigin under" the conditions presently considered "'nbrmar for highway and railroad movement.

-In the event it is desired to gain access to the interior of the assembly'for inspection, maintenance orrepairs liquid coolant remaining in 'tank ll maybe rapidly discharged by removing cap 37 from nozzle 38located on the top of exterior shell 10, removing the insulation from within that nozzle, removing cap 39from nipple," 40 disposed above 'T 41 into which coolant chargefcon duit 30 leads and then insertinga flexible discharge lance through nipple 40, T 41 and nipple 42 into tank lland around fluorine tank 12 to the bottom of tank 11. Thecoolant may then be discharg d as liquid'from' tank 11 either by aspiration through theflex'ible' lance orby application of pressure or air or othersuitable gas through coolant feed line 30'. -To discharge fluorine from the tank assembly, after transportation or the desired periodot storage-agar inert with respect to and'lo'wer boiling than fluorine and the coolant, for example, helium, supplied from a suitable source (not shown) is, forced at preferably slight superatmospheric pressurethrough fluorine charge inlet 23 and charge conduit 24 to expel the liquid fluorine through discharge conduit 26 and discharge'outlet 25 connected to a suitable receptacle (not shown). After the: liquid fluorine is discharged, it is preferred to" seal the displacing gas within tank 12'by closing the inlet and outlet valves 24a and 26a. Th'eri, priorto recharging t re tank with fluorine, tank 12 is evaucated as 'by a vacuum pump connected to inlet 23 or outlet 25 until.

the pressure within the'tank at liquid coolant tempera ture is reduced to below half an atmosphere and preferably to approximately that of the liquid fluorine at that temperature. andpreferably is retained for future use,

A typical assembly used in practice of the invention comprises a three-shell tank 'unit' weighing about 4,000 pounds empty mounted on 'a' truck trailer, the tank portion of which exclusive of service piping and instruments has an overall length of somewhat over 11 feet, a diameter of about '6" and total volume of about 1350 gallons. Disposed within it is an intermediate or nitrogen tank having an overall length of about 9'6", a diameter of 4. feet and volume of about 7l0'gallons to leave an intervening evacuated space of somewhat. under 9" filled with perlite. Within the nitrogen tank, equidistantfrorn its ends and about 2"- below its center line, is a fluorine tank of about 42 diameter and 7T3'fin length, having a volumetric capacity of=460gallons A one, inch pipe size fluorine charge line of about 30 feet total length connects the fluorine charge inlet and the top of the fluorine tank, about 22 feet of this length being in the form of a hairpin curve extending around one end of the tank below its center line and completely immersed in liquid nitrogen when filled to the center line of the nitrogen tank. A fluorine discharge conduit of the same diameter communicates with the bottom interior of the fluorine tank. This unit is capable of being The evacuated discharging gas may be charged'with up to about five thousand pounds of fluorine flowing from a gaseous fluorine source maintained at pressure of two to three pounds per square incbgauge intothe evacuated tank therefor, at rate of upwards of 800 pounds per hour, while admitting nitrogen during the charging period at overall rate of one and one-quarter to one and one-half pounds per pound of fluorinei When the nitrogen tank is filled with nitrogen (about two hundred forty gallons), the assembly is capable of maintaining a full charge of liquid fluorine at pressure of about five pounds per square inch absolute without loss andwithout additional nitrogen charge at ambient temperatures of F. and even above for periods of thirty to thirty-five days. It discharges readily at rates at least as high as the rates of charge.

i We. claim as our invention: 7

1. The process of handling fluorine in bulk comprising leading gaseous fluorine charge through an extended pas sage'way in indirect heat exchange relation with a body of liquid coolant boiling below the boiling point of fluorine until said charge is condensed and thence into an evacuated storage volume maintained in indirect heat exchange relation with said body, and subsequently displacing said liquid fluorine from said volume by admitting to said volume a gas inert with respect to fluorine and? lower boiling than said coolant.

2. The process of handling fluorine in bulk comprising providing an evacuated storage volume therefor provided with an outlet communicating with its bottom and with an inlet, leading gaseous fluorine until condensed through an extended passageway in indirect heat exchange rela-' tion with a body of liquid coolant lower boiling than fluorine'and thereafter into said volume, maintaining saidliquid fluorine in indirect heat exchange relation with said body and under subatmospheric pressure for a desiredperiod of storage, and discharging said fluorine from saidvolume at the end ofsaid period by admitting to said volume a gas lower boiling than said coolant and inert with respect to fluorine to force the liquid fluorine through said outlet.

"3. The process of handling in bulk fluorine supplied in gaseous form at approximately atmospheric pressurev involving storage of the fluorine and its subsequent discharge from storage comprising conducting fluorine charge in gaseous form in indirect heat exchange relation with a body of liquid coolant lower boiling than fluorine until condensed and cooled to liquid form having vapor pressure not above about half an atmosphere, conducting said cooled liquid fluorine into a closed storage volume maintained in indirect heat exchange relation with saidbody of coolant and at substantially the aforesaid sub atmospheric vapor pressure, storing said fluorine in said volume in indirect heat exchange with said body of coolant while maintaining said volume sealed and at said! s'ubatmospheric pressure, subsequently connecting said volume at its bottom with a receptacle for fluorine, and; displacing said fluorine from said volume by admitting tame latter a gas lower boiling than said coolant and inert with respect to said fluorine, and effecting movement of-fluorineduringcharging it into and displacing it from said volume solely by the respective pressures of gaseous fluorine charge and of the aforesaid inert gas.

4.'Process according to claim 3 wherein isnitrogen and theinert gas is helium.

'5? Thefprocess of'h'andling in bulk fluorine supplied the coolant} in gaseous form 'at approximately atmospheric ressure enemas subatmospheric vapor pressure, whereby said coolant is evaporated, venting coolant from said body thereof to the atmosphere, adding coolant to the evaporating body, storing said fluorine in said volume in indirect heat exchange relation with said body of coolant while maintaining said volume sealed and at said subatmospheric pressure, subsequently connecting said volume at its bottom with a receptacle for fluorine, and displacing said fluorine from said volume by admitting to the latter a gas lower boiling than said coolant and inert with respect to said fluorine, and eflecting movement of fluorine during charging it into and displacing it from said volume solely by the respective pressures of gaseous fluorine charge and of the aforesaid inert gas and while venting said body of coolant to the atmosphere.

6. The process of handling in bulk fluorine supplied in gaseous form at approximately atmospheric or somewhat higher pressure involving storage of the fluorine and its subsequent discharge from storage comprising cooling a closed storage volume for the fluorine to substantially the boiling point of nitrogen by surrounding said volume with a body of boiling liquid nitrogen, reducing the pressure of said closed storage volume to sub-. stantially the vapor pressure of fluorine at the boiling point of nitrogen, conducting gaseous fluorine as supplied through an elongate passageway extending through but immersed in said body of liquid nitrogen to condense the fluorine and cool it to substantially the temperature of said body of liquid nitrogen, admitting the liquefied and cooled fluorine to said closed storage volume adjacent the top thereof, venting said body of nitrogen to the atmosphere during admission of fluorine to said volume, admitting liquid nitrogen to said body to maintain said passageway immersed therein, terminating the flow of fluorine, sealing said volume and storing said fluorine therein and in indirect heat exchange relation with said body While venting said body to the atmosphere, subsequently displacing the stored liquid fluorine from said volume through the bottom thereof by admitting helium to the top thereof. 7

7. A tank assembly for storage of liquid fluorine comprising, in combination, an outer tank having insulation therearound, an inner tank Within and spaced from said outer tank providing intervening volume for liquid coolant lower boiling than fluorine, a valved inlet for gaseous fluorine and a valved outlet for liquid fluorine disposed outside said outer tank, a fluorine discharge conduit interconnecting the bottom of said inner tank with said valved outlet, a fluorine charge conduit interconnecting said valved inlet with the upper portion of said second tank,

said charge conduit providing within said intervening volume an elongate passageway of length suflicient to eflect condensation of and to cool to substantially the temperature of said liquid coolant gaseous fluorine flowed therethrough from said valved inlet, a valve inlet for liquid coolant disposed outside said outer tank, a conduit interconnecting said last named valved 'mlet and said intervening volume, and means venting said volume to the atmosphere.

8. A tank assembly for storage of liquid fluorine comprising, in combination, an outer tank having insulation, therearound, an inner tank within and spaced from said outer tank providing intervening volume for liquid coolant lower boiling than fluorine, a valved Inlet for gaseous fluorine and a valved outlet for liquid fluorine disposed outside said outer tank, a fluorine discharge con-' duit interconnecting the bottom of said inner tank with said valved outlet, 8. fluorine charge conduit interconnecting said valved inlet with the upper portion of said second tank, said fluorine charge conduit providing with: in said intervening volume and within the lower portion thereof an elongate heat exchange coil of length sufficient to elfect condensation of and to cool to substantially the temperature of said liquid coolant gaseous fluorine flowed therethrough from said valved inlet, a valved inlet for liquid coolant disposed outside said outer tank, a conduit interconnecting said last named valved inlet and said intervening volume, and means venting said volume to the atmosphere.

9. A tank assembly for storage of liquid fluorine comprising, it combination an outer tank having insulation therearound, an inner tank within and spaced from said outer tank providing intervening volume for liquid coolant lower boiling than fluorine, a valved inlet for gaseous fluorine and a valved outlet for liquid fluorine disposed outside said outer tank, a fluorine discharge conduit interconnecting the bottom of said inner tank with said valved outlet, a fluorine charge conduit interconnecting said valved inlet with the upper portion of said second tank, said conduit providing within said intervening volume and in the lower portion thereof an elongate section of length at least half the length of the periphery of said inner tank and sufi'icient to effect condensation of and-to cool to substantially the temperature of said liquid coolant gaseous fluorine flowed therethrough from said valved inlet, a valved inlet for liquid coolant disposed outside said outer tank, a conduit interconnecting said last named valved inlet and said intervening volume, and means venting said volume to-the atmosphere.

10. The process of charging fluorine to bulk storage comprising providing a closed storage volume therefor,

cooling said volume to temperature at least as low as C. by maintaining the same in indirect heat exchange relation with a body of coolant liquid boiling not above 190 C., adjusting the pressure of said storage volume to about the subatmospheric pressure corresponding to vapor pressure of fluorine at the boiling point of said coolant, supplying gaseous fluorine at atmospheric or slightly higher pressure, flowing a stream of gaseous fluorine as supplied through said body of coolant liquid and in indirect heat exchange relation therewith until the fiuorine is condensed and cooled to ap proximately the boiling point of said coolant thereby causing the coolant to evaporate, venting evaporated coolant to the atmosphere to maintain said body at substantially atmospheric pressure, simultaneously admitting liquid coolant to said body at overall rate suflicient to maintain the body in indirect heat exchange relation with said volume and said stream of fluorine, and effecting the flow of fluorine through said body and into said volume solely by the pressure of supply thereof.

11. Process according to claim 10 wherein the cool ant liquid is nitrogen.

References Cited in the tile of this patent UNITED STATES PATENTS 1,680,873 Lucas-Girardville Aug. 14, 1928 1,894,497 Rowland Jan. 17, 1933 2,148,109 Dana Feb. 21, 1939 2,525,802 Joerren Oct. 17, 1950 2,834,187 Loveday May 13, 1958 2,863,297 Johnson Dec. 9, 1958 

1. THE PROCESS OF HANDLING FLUORINE IN BULK COMPRISING LEADING GASEOUS FLUORINE CHARGE THROUGH AN EXTENDED PASSAGEWAY IN INDIRECT HEAT EXCHANGE RELATION WITH A BODY OF LIQUID COOLANT BOILING BELOW THE BOILING POINT OF FLUORINE UNTIL SAID CHARGE IS CONDENSED AND THENCE INTO AN EVACUATED STORAGE VOLUME MAINTAINED IN INDIRECT HEAT EXCHANGE RELATION WITH SAID BODY, AND SUBSEQUENTLY DISPLACING SAID LIQUID FLUORINE FROM SAID VOLUME BY ADMITTING 